Preheat the oven to 350 degrees.

Grease and flour two 8 inch round pans. Combine all ingredients and beat with hand mixer until smooth and combined.

Divide the batter between the two pans.

Bake in the preheated oven for 21 minutes, or until a toothpick inserted into the center of the cake comes out clean.

Allow to cool in pans on wire racks for 10 minutes. Then invert onto wire racks to cool completely.

In a medium saucepan, mix together 1 tablespoon lemon zest, 1/2 cup lemon juice and 1 tablespoon cornstarch until smooth.

Mix in 6 tablespoons butter and 3/4 cup sugar, and bring mixture to boil over medium heat.

Boil for one minute, stirring constantly.

In a small bowl, with a wire whisk, beat egg yolks until smooth.

Whisk in a small amount of the hot lemon mixture.

Pour the egg mixture into the saucepan, beating the hot lemon mixture rapidly.

Reduce heat to low; cook, stirring constantly, 5 minutes, or until thick (not to boil).

Pour mixture into a medium bowl.

Press plastic wrap onto the surface to keep skin from forming as it cools. Cool to room temperature. Refrigerate 3 hours.

In a standing mixer, beat powdered sugar, 1/2 cup butter, heavy whipping cream, 2 tablespoons lemon juice and 1 teaspoon lemon zest until smooth, and increase speed and continue to beat until light and fluffy

Using a cake leveler, split each cake layer in half horizontally, making 4 layers.

Place 1 layer, cut side up, on a serving plate.

Spread with half of the lemon filling.

Top with another layer, and spread with 1/2 cup frosting.

Add the third layer, and spread with the remaining half of the lemon filling.

Place the last layer of cake on top.

Scoop remaining frosting into the piping bag and pipe dollops completely covering the cake.